Flex lead on cell container for electromagnetic shielding

ABSTRACT

A battery system has a battery cell including a can and tabs, flexible circuits on and electrically isolated from the can, and electrically connected with the tabs, and a monolithic integrated circuit. The monolithic integrated circuit is mounted to the can via thermally conductive adhesive such that the can and monolithic integrated circuit are electrically isolated from one another. The monolithic integrated circuit is also wire bonded to the flexible circuits, and configured to measure and transmit data about the battery cell.

TECHNICAL FIELD

This disclosure relates to battery cells having flexible circuitry andintegrated circuits thereon.

BACKGROUND

Electrified vehicles, such as battery electric vehicles andhybrid-electric vehicles, may include a traction battery that powers anelectric motor for propulsion. The traction battery may be controlledaccording to data about cells of the traction battery. Circuitry can beused to obtain this data.

SUMMARY

A battery system has a battery cell including a can and tabs, flexiblecircuits on and electrically isolated from the can, and electricallyconnected with the tabs, and a monolithic integrated circuit. Themonolithic integrated circuit is mounted to the can via thermallyconductive adhesive such that the can and monolithic integrated circuitare electrically isolated from one another. The monolithic integratedcircuit is also wire bonded to the flexible circuits, and measures andtransmits data about the battery cell.

A battery system has a battery cell including a can and tabs, flexiblecircuits on the can and electrically connected with the tabs, andcircuitry adhered to the can, wire bonded to the flexible circuits, andthat measures and transmits data about the battery cell.

A battery system has a battery cell, flexible circuitry on andelectrically isolated from a container of the cell, and electricallyconnected with terminals of the cell, and an integrated circuit adheredto and electrically isolated from the container, wire bonded to theflexible circuits, and that measures and transmits data about thebattery cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a battery pack with N cells in series.

FIG. 2 is a schematic diagram of one of the substrate boards of FIG. 1.

FIG. 3 is a schematic diagram of the power switch, reference, and cellbalance circuit of FIG. 3.

FIG. 4A is a perspective view of a battery cell system.

FIG. 4B is a side-view, in cross-section, of a portion of the batterycell system of FIG. 4A.

FIGS. 5 and 6 are side views of battery cell systems.

FIG. 7 is a side view, in partial cross-section, of a battery cellsystem.

FIG. 8 is a schematic diagram of a battery monitoring integratedcircuit.

FIG. 9 is a schematic diagram of one of the pass switch circuits of FIG.8.

FIG. 10A is a side-view, in partial cross-section, of a battery cellsystem.

FIG. 10B is a top view of a portion of the battery cell system of FIG.10A.

DETAILED DESCRIPTION

Various embodiments of the present disclosure are described herein.However, the disclosed embodiments are merely exemplary and otherembodiments may take various and alternative forms that are notexplicitly illustrated or described. The figures are not necessarily toscale; some features may be exaggerated or minimized to show details ofparticular components. Therefore, specific structural and functionaldetails disclosed herein are not to be interpreted as limiting, butmerely as a representative basis for teaching one of ordinary skill inthe art to variously employ the present invention. As those of ordinaryskill in the art will understand, various features illustrated anddescribed with reference to any one of the figures may be combined withfeatures illustrated in one or more other figures to produce embodimentsthat are not explicitly illustrated or described. The combinations offeatures illustrated provide representative embodiments for typicalapplications. However, various combinations and modifications of thefeatures consistent with the teachings of this disclosure may be desiredfor particular applications or implementations.

Referring to FIG. 1, battery pack 10 contains a series stack of cells 12starting at the lowest cell in the string, Cell 1, 14, which isconnected to Cell 2, and so on up to Cell N, which is the top cell inthe string. Here, the N cells are series connected. This is a usualarrangement for cells in a full hybrid, which could be described as“Ns1p,” which means a cell string just one cell wide or “1p” with N ofthese “1p” units stacked on top of each other. As an example, N may be60 for a full hybrid, so 60s1p would describe these 60 cells in one longseries string, and nothing in parallel. Now if one had a string whichwas 2 cells wide, or “2p” and if there were 120 cells available, and themost basic unit is 2 cells in parallel or “2p,” then it is possible tostack in series 60 groups of two cells in parallel. In this instance,when we stack all 2-cell parallel groupings in series on top of eachother, called 60s2p, the resulting pack has the same voltage as 60s1p(for which the pack voltage is the nominal cell voltage times 60), butthe pack's capacity is double that of a 60s1p.

From the perspective of the battery electronics hardware, a packarrangement of 60s1p works the same as 60s2p, since there are still just60 voltages to be measured. The reason for this is because for each ofthe 2 cells placed in parallel, only one voltage needs to be measured.Since there are 60 series-stacked instances of the 2p parallel unit,there are 60 voltages overall to be measured in the whole pack. Theordinary arrangement for a battery electric vehicle might be to use, forinstance, a series combination of 96 voltages to be read wherein eachunit is 5 cells in parallel, which would be a 96s5p. The total number ofcells for this example battery electric vehicle is 96*5=480 cells.Notice that what is proposed works for any type of electrified vehicle,and while FIG. 1 specifically depicts the situation with N cells inseries, this approach works regardless of the width “in parallel” of thepack-which means that a Ns1p has the same hardware setup as a Ns5p, forexample.

The battery pack 10 could be for any sort of an electrified vehicle,ranging from mild hybrid, value hybrid, full hybrid, plug in hybrid,battery electric vehicle, or any other sort of vehicle that needs atraction battery that calls for the monitoring of individual cellvoltages (although again, for cells that are in parallel with eachother, only one voltage needs to be measured). A noteworthy feature isthe existence of a small substrate board 16, which is a small circuitassembly, on FR4, ceramic, or some other suitable material, thatcontains the circuitry needed for sensing the voltage and temperature ofthe cell 14 and transferring this information over an RF Link 18 betweenthe substrate board 16 and a central battery energy control module(BECM) 20. The RF link 18, which is implemented with radio frequencycommunications, may use a purely wireless medium between the substrateboard 16 and central module 20, using antenna emissions from thesubstrate board 16 coupling energy to a receiving antenna on the BECM20, or it may use the medium of the high voltage bus in the battery pack10. For instance, the cell string 14 as mentioned above is connected ina series string. The (−) terminal on Cell 1 could be referred to asV_BOT 22, which means the lowest potential of the cell string 14. Thissame node is connected through a wire 24 to the V_BOT node of the BECM20. Similarly, the (+) terminal of Cell N is connected to a nodereferred to as V_TOP 26. This node is connected to the BECM 20 through awire 28 to the V_TOP terminal of the BECM 20. In this fashion, the BECM20 is connected to the high voltage bus coming from the cell stack 14consisting of all cells from Cell 1 to Cell N. Since both the cellstring 12 and BECM 20 are connected to the same high voltage bus 24, 28they can use the high voltage bus 24, 28 as a medium that allows RFenergy to travel from the substrate board 16 (or any of the othersubstrate boards), through the wiring connecting all the cells to eachother, through the high voltage bus wiring 24, 28 and to the BECM 20.This high voltage bus is a wired medium, but this wired medium may alsocarry RF energy from the substrate board 16 (or any other the othersubstrate boards) to the central module 20. In fact, for the radiofrequency link between a given substrate board to the central module 20,some fraction of the signal energy may travel through antenna radiation18, and some other fraction of the signal energy may travel through thehigh voltage bus 24, 28. Accordingly, the system designer will arrangethe RF communication circuits on substrate boards and the matching RFcommunication circuits in the BECM 20 in such a way that RF propagationmight happen in any proportion between the wired high voltage bus linkfrom the cell string 14 to the V_TOP and V_BOT pins on the BECM 20, orin the wireless medium between the substrate board 16 and BECM 20.

It should be noted that any substrate board may communicate using the RFlink 18. That is, the RF communication circuit on the substrate board 16not only can communicate with the BECM 20, but also can communicate viaRF to any other substrate board in the same pack. The same discussionabove regarding the possibility of using a wireless medium between thetwo communicating substrate boards, or of using the high voltage busthat connects the given two communicating substrate boards, applies. Nowin practice, each substrate board might be able to best reach nearbysubstrate boards using an RF link, but may have a more difficult timereaching faraway substrate boards for numerous reasons such as signalstrength, the efficiency of the RF channel between the sending andreceiving substrate board, and so on. Therefore, a method known as meshnetworking is employed, wherein the route that a message takesprogressing from one substrate board to the central BECM 20 may takeseveral hops, which means that the originating substrate board sends outa message on the RF link to another nearby substrate board, and it willforward it to a substrate board which is closer to the central BECM 20and so on, until the message reaches a substrate board which has anexcellent RF link with the BECM 20. At that point, the message is sentfrom the last substrate board in the mesh link to the central BECM 20.The process can work in reverse, wherein the central BECM 20 sends amessage to a nearby substrate board, and then the messages is forwardedalong multiple links using the same sort of mesh networking concepts,until the message arrives at the board which is addressed in themessage. For a system that is properly set up to utilize meshnetworking, there is no functional difference between a situation inwhich a given substrate board has a direct RF link between itself andthe central BECM 20, and a situation where the communicating substrateboard should mesh network with a number of hops equal to the number ofsubstrate boards in the battery pack 10. Now, it is conceivable that thehop limit, or the number of hops that a message can traverse beforebeing discarded, could be set to larger than the number of substrateboards in the battery pack 10. However, this approach may lead toinefficient use of the RF spectrum considering that every time meshnetworking is employed to pass a message from one substrate board toanother substrate board, a certain amount of the available RF spectrumis used up. That is, if at a given moment in time a substrate board hasan available link to the central BECM 20, and it has a message which isaddressed to the BECM 20, it should preferentially send that message tothe BECM 20 rather than forward it to some other substrate board nodewhich will continue the usage of the mesh networking mechanism and aswell, continue to consume RF spectrum. The most efficient usage of theRF spectrum will occur in situations where mesh networking is not neededat all, for instance in a system wherein each substrate board node isalways able to transmit and receive messages directly from the centralBECM 20. But, since this is not always the case, the system can be setup with mesh networking capability so that if under some circumstances asubstrate board may not be able to directly reach the BECM 20 through anRF link, the message can be sent to a nearby substrate board to utilizemesh networking. This usage of mesh networking concepts inside thebattery pack 10 is why this technology may be called battery packsensing module peer to peer, which means that a network is formed amongthe peer substrate boards to overcome any deficiencies in the RF linkfrom a given substrate board to the central BECM 20.

There are a few other items in FIG. 1 worth mentioning. Positive maincontactor MC+ 30 connects (and disconnects) the cell string 14 to therest of the vehicle as node HV+ 32 is under the control of the BECM 20.That is, the BECM 20 has a contactor drive circuit, connected to thecoil of the MC+ contactor 30, that can open and close the MC+ contactor30 under the control of software executing in the BECM 20. In a similarfashion, negative main contactor MC− 34 connects the lowest potential inthe cell string 14 to vehicle HV bus node HV− 35 under the control ofsoftware executing in BECM 20. A feature of the battery pack 10 is topre-charge the HV bus before closing the main contactor MC+ 30.Pre-charge contactor PRC 36 and pre-charge resistor 38 are utilized forthis HV bus pre-charge.

A typical contactor close sequence, to progress the battery pack 10 fromall contactors open to having the HV bus 32, 35 connected, would be tofirst close the MC− 34 and PRC 36 at the same time, which willpre-charge the HV bus 32, 35 through the pre-charge resistance PRC 38.The BECM 20 can monitor the voltage on the vehicle HV bus 32, 35. Whenthis HV bus voltage is close in voltage to the pack voltage V_TOP 26with respect to V_BOT 22, for instance within 20V, then pre-charge issuccessful and the MC+ 30 can be closed. It should be noted that theBECM 20 is on the vehicle CAN bus 40 and through the CAN bus 40communications occur between the BECM 20 and the rest of the vehicle.Other modules in the vehicle make the determination when it is desiredto connect the high voltage traction battery pack 10 to the HV bus 32,35 and they send CAN messages through the vehicle CAN bus 40 to the BECM20. The BECM 20 uses the vehicle CAN bus 40 to coordinate with the othermodules in the vehicle.

Referring to FIG. 2, we discover lower level details about the substrateboard 16, which can be made of a suitable substrate material such as FR4or ceramic as mentioned above. It may be desirable to make the substrateboard 16 as small, reliable, and inexpensive as possible since thevehicle bears the cost of N of these substrate boards for N cells (inthe event of a single series string such as Ns1p configuration.)Ideally, all the functions and circuits depicted on FIG. 2 would be ableto be contained in a single monolithic piece of silicon, to reduce costand improve reliability. However, there are many reasons which wouldlead to a small number of components to be mounted on the substrateboard 16. The first reason that more than one component may be needed onthe substrate board 16 is because of the crystals 42 and 44. The crystal42, for example 24 MHz, may be used to regulate the frequency used inthe RF circuit. This 24 MHz crystal may be used with a phase locked loop(PLL) to multiply the oscillations to obtain an RF carrier frequency.The 24 Mhz oscillations may also be subdivided down via a digitalcircuit as needed if the RF carrier is desired to be lower than 24 Mhz.On the other hand, the crystal 44, for example 32.768 kHz, may be usedas a low power real time clock (RTC). This type of crystal is called awatch crystal and is common for circuits that need to keep time. Thecrystal 44 is optional in certain implementations because the processor46 may have a simple low power RC oscillator built in that is able tokeep time when the circuits on the substrate board 16 are sleeping. Thekey difference between the use of the optional watch crystal 44 and abuilt-in RC oscillator in the processor 46 is that the watch crystal 44is quite accurate, for instance +−20 PPM. This level of accuracy willonly lead to about 12 seconds of error per week. However, if theinternal RC timer inside the processor 46 is used, the accuracy is about8 percent. An application for which excellent accuracy during sleep isrequired would be if the substrate board 16 is sleeping most of thetime, and wakes up exactly at the right moments to transmit data aboutCell 1. The idea is that all the cells in a pack from 1 to N would besleeping and each one would wake up at just the right moment into orderto transmit in the correct timeslot. This approach leads to the lowestcurrent draw from each cell.

All the power to run the electronics on the substrate board 16 comesfrom Cell 1. If the goal is to minimize current consumption from thecell, then it would be considered advantageous to minimize the currentdraw and sleeping most of the time would accomplish this. However, it istrue that when an electrified vehicle is charging or driving, it is nota problem to have the system put energy into the traction battery, andthere is no special need to minimize the current draw from the substrateboard 16. For example, if the average current can be held at 10 mA orless, this would be a typical current load on, for example, a lithiumbattery as imposed by a typical battery monitoring integrated circuit.The amount of operating current draw from this type of monitoringelectronics is not a problem to the system. What can be a problem to thesystem is if the operating currents differ from one cell to the next.When the current draw is different from one cell to the next, then thecell balancing feature of the substrate board comes into play.

To sum up the concept for the optional watch crystal 44, the choice toinclude a watch crystal will be related to the desire to minimize thecurrent draw out of the cells by having the electronics sleep most ofthe time, except during the moments when the radio in the circuit block46 is transmitting. However, many applications will be able to leave thepower applied to the substrate board 16 when the battery pack 10 isoperating and utilize the relatively accurate clock offered by thecrystal 42. The crystal 42 will be utilized when the substrate board 16is transmitting and therefore is drawing full power.

Another optional choice for the system is a precision reference that iscontained in the cell balance, power switch, and reference circuit 48.This precision reference is the “reference” in the circuit 48. Now, someapplications will need better accuracy than others. For example, a fullhybrid electric vehicle application tries to keep the cells within theoperating window of 30% state of charge (SOC) to 70% SOC for example,and never tries to charge the pack up to exactly 100% SOC. However, aplug-in vehicle will of course try to charge each cell in the pack up toexactly 100% SOC. The reason why a plug-in vehicle wants to have eachcell at exactly 100% SOC at the end of a charge is that in soaccomplishing this, the vehicle will have the maximum range while notjeopardizing the cell. Within certain bounds, this is tantamount tosaying that the more accurate the cell voltage can be measured in thefunction of determining the end of charge condition, the more capacitythe pack can have. (Or, the more inaccurate the cell voltage ismeasured, the more margin needs to be placed on the threshold voltageused in determining 100% SOC for a given cell.) So, for a large pack, itmay well make sense to pay for a precision reference in the circuit 48to develop a precision reference voltage for the substrate board 16. Asan example, the choice of the reference voltage in the circuit 48 andthe accuracy of the A/D conversion (or voltage measurement function) inthe circuit block 46 may be specified to be able to determine thevoltage of Cell 1 to within ±10 mV under all conditions, which would befairly accurate for a plug-in application. It is the case that a fullhybrid electric vehicle application may be able to get by with lessaccuracy than this, for example, ±100 mV. So, if a common hardwaredesign is created for the substrate board 16, in order to accommodatethe more accurate plug-in application, the circuit 48 may populate aprecision bandgap reference in the generation of a precision referencevoltage which comes out of the block 48 and is presented for use in thecircuit block 46 by its voltage measurement function. However, a batterypack manufacturer may elect to depopulate the precision reference in thecircuit 48, thereby not generating a precision voltage. This would becoordinated with a software change in the circuit block 46 so thatinstead a different, lower accuracy reference inside the circuit block46 is used. This choice is a tradeoff between the costs of the substrateboard 16 and the need for accuracy by the application. In sum, the watchcrystal 44 can be optional depending on the need for timekeepingaccuracy in sleep by the application, (and as well, bandgap reference 50in FIG. 3 is optional depending on the need for cell voltage measurementaccuracy by the application).

A few more comments can be made regarding the high-level blocks in thesubstrate board circuits. Cell 1 is the item being measured, and thevoltage of cell 1 is an input to the block 48. Also, the substrate board16 is powered from the same two nodes that connect to cell 1. There is avoltage Vsns which comes out of the circuit 48 and goes into the circuitblock 46. This Vsns voltage is intended to be the same voltage as thepositive lead of cell 1. Vpwr, coming out of the circuit 48 and goinginto the circuit block 46, is the power supply to run the processor,radio, etc. This power supply can get interrupted (intentionally) if thecircuit block 46 asserts the functional safety watchdog (FSWD) signalFSWD. The purpose of the FSWD is to be able to shut down the powersupply if it is determined the substrate board 16 is not workingcorrectly, which is an implementation of a complete power down for thecircuit block 46. This type of complete power down is intended torestore the substrate board 16 to its boot-up state. If the FSWDindicates a problem, the recourse is to power down the processor.

The circuit block 46 contains the processor, a radio, and what isreferred to as auxiliary functions. The auxiliary functions include theA/D conversion of the cell voltage attached to the substrate board 16via the Vsns input to the circuit block 46, a general purpose digitalinput/output port used as a digital output for activating the cellbalance function for the substrate board 16, also referred to as CBctl,and the FSWD. The FSWD output is operated by a circuit in the auxiliaryfunctions which is designed to pulse when the processor software isdetected to not be operating properly. This pulsing of the FSWD outputof the processor, to the FSWD input of the block 48, will cause theblock 48 to interrupt the power supply long enough to guarantee acomplete power down of the processor in the circuit block 46. The block48 is designed in such a fashion that even if the circuit block 46 isfaulted and leaves the FSWD output permanently asserted, the powercircuits such as Vpwr and Vref will be able to operate. The function ofthe block 48 is arranged so that the Vpwr and Vref are turned off onlyfor a fixed duration in time, for example 100 mS after a pulse on theFSWD output on the circuit block 46. So, Vpwr provides the power tooperate the processor, auxiliary circuits, and radio in the circuitblock 46. Vsns is the same potential as Cell 1, and an auxiliaryfunction of the circuit block 46 is to perform an A/D conversion on thisvoltage Vsns, which results in the measurement of the cell voltage,which is a primary function of the substrate board 16. The circuit block46 utilizes the Vref input in this A/D conversion function.

As mentioned above, the precision bandgap reference 50 in FIG. 3 isoptional; and if it is depopulated, then the Vref signal from the block48 is invalid. When Vref is invalid, the circuit block 46 is engineeredto automatically switch over to its own internal, and less accurate,reference. The CBctl digital output from the circuit block 46 is underthe control of software that runs on the processor in the circuit block46. As mentioned above, the crystal 42 used for the RF communicationsfrom the circuit block 46. The crystal 42 is also used as a system clockfor the processor in the circuit block 46. The crystal 44 is optionaland is a watch crystal used for a low power real-time clock to keepaccurate time when the processor in the circuit block 46 is sleeping, ifthis is useful for the application. If this feature is not needed, thecrystal 44 may be depopulated. Signal RFtxrx coming from the circuitblock 46 is from the radio in circuit block 46. It is a bidirectionalsignal which can function as a transmitted signal coming from the radio,or as the input signal to the radio. As alluded to earlier, the RFtxrxsignal is connected through a coupler circuit 54 to both the power linecarrier (PLC) bus interface 56 which is to the (+) cell input to thesubstrate board 16, which is the high voltage bus of the battery pack10; and at the same time, the RFtxrx is connected to antenna circuit 58.This simultaneous connection to both the antenna circuit 58 and the HVbus 32, 35 through the coupler circuit 54 allows a fraction of thesignal energy to travel out on the HV bus 32, 35, and a fraction to exitthe substrate board 16 through the wireless antenna 58. Similarly,received energy can enter the substrate board 16 either through the HVbus 32, 35 or through the antenna 58. That is, RF energy from the block46 is directed to the coupler circuit 54. The coupler circuit 54 canthen selectively direct that energy to either or both the antennacircuit 58 and PLC bus interface 56, which is the gateway to driving theRF energy on the high voltage bus 32, 35 for communication with othersubstrate boards for other cells, and the vehicle more generally. Thecoupler circuit 54 is frequency selective in that it may lower thefrequency content associated with the RF energy to permit it to flow tothe PLC bus interface 56.

Referring to FIG. 3, the details of the power supply portion arerevealed. The cell input to the substrate board 16, for instance cell 1,are attached through Cell+ lead 60 and Cell− lead 62. Interestingly,these 2 pins are the only wired interface between the substrate board 16and the rest of the system. The only other interface to the system iswireless RF communications. A certain amount of RF energy is intended totravel through the connections 60 and 62. Also, the power to operate thesubstrate board 16 is drawn from the individual cell and flows throughthe connection 60 (+) and connection 62 (−). It should be observed thatthe node 60 or cell+ is connected through current limiting resistor Rlim64 and connected the Vsns, which goes over to the circuit block 46 formeasurement. It should be noted that the potential at the node Vsns iswith respect to the node 62, which is the ground reference for theentire substrate board 16.

The node 62 is locally grounded. Generally, any circuit in the substrateboard 16 that needs a ground reference will use the node Cell− 62. Thecell balancing functionality of the block 48 is implemented by switchSWcb 70, which may be implemented with a N-channel MOSFET. Burdenresistor Rcb 72 completes the cell balance circuit. Notice that if thesignal CBctl which comes from the circuit block 46 is active, then theSWcb 70 activates, which connects the Rcb 72 across the cell 14 throughthe connections 60, 62, thereby applying a passive ohmic load of acertain amount, for example 8 mA. This current is referred to the as thecell balance capability of the substrate board 16 and it can easily beset by adjusting the ohmic value of the Rcb 72. However, the powerdissipated goes as (Vcell{circumflex over ( )}2)/Rcb, where Vcell is thevoltage of the cell 14.

Control block 80 is shown which controls a pass switch 82. For instance,the pass switch 82 could be implemented as a P-channel MOSFET. Thehigh-level details for the control block 80 are mentioned here, whichcan readily be implemented by one skilled in the art. The cell voltagefrom connections 60, 62 is read by a connection from the control blockthe 80 to the node 60. This allows the control block 80 to act when Cell1 is too low in voltage, for instance by opening the pass switch 82. Aswell, the control block 80 reads in the FSWD command signal from thecircuit block 46. This signal will pulse when the circuit block 46 wantsto command a momentary power shutdown to perform a hardware restart ofthe system. However, if the FSWD 48 stuck in the active state owing to afault, the control block 80 will turn the pass switch 82 on to allow thesubstrate board 16 to operate. However, the processor in circuit block46 will need to detect that the FSWD feature is not working. One methodis to set a digital “1” in some register that is known to assume a “0”value any time the processor resets. When the FSWD activates, thesoftware can ascertain if the memory location remains 1, which meansthat the power never got shut off and the FSWD did not work. When theFSWD does not work, diagnostics need to be set and the central moduleBECM 20 should be notified of the hardware issue. The basic feature ofthe control block 80 is that if the cell voltage is normal and the FSWDsignal has not pulsed, then it activates the pass switch 82 to connectpower to Vpwr and to active Vref. Note that the bandgap reference 50 isarranged in conjunction with resistor Rpu 90, for example 1.8 kohms, tocreate the reference voltage Vref when the pass switch 82 is activated.

Referring to FIGS. 4A and 4B, the mounting scheme for the substrateboard 16 on the cell 14 is shown. A thermally conductive material suchas a thermal epoxy or SIL-PAD 76 is between the substrate board 16 andthe cell top in certain implementations. To the extent additional poweris dissipated in the cell balance circuit 70, 72, it is important thatthis heat be removed from the substrate board 16 through the thermalbond 76. Container or can 78 of the cell 14 has a reasonable amount ofsurface area, and so it may be able to directly dissipate the heatgenerated in the cell balance circuit 70, 72. However, if the can 78cannot dissipate this heat, then some sort of cooling mechanism, such asair or liquid cooling, should be devised to keep the cell 14 cool.

The substrate board 16 is mounted on the cell 14 with thermal connection76 (e.g., thermal epoxy) to allow heat removal from the substrate board16. The cell 14 needs to have its voltage and temperature measured andthe data wants to be sent to the central BECM 20. The substrate board 16is encapsulated in a protective material and mounted on top of a can 78of the cell 14. Flex cables 94, 96 are soldered to the substrate board16 and come out of the packaged substrate board on opposite sides. Theflex cable 94 is weld attached to cell tab 98, which is the positiveterminal of the cell 14. The flex cable 96 is weld attached to cell tab100, which is the negative weld tab of the cell can 78. The flex cable94 is fastened tightly at both ends, and may be adhesively connected tothe cell can 78. Generally, the flex cable 94 should be insulated toavoid shorts to the cell casing 78. The same comments apply to the flexcable 96. Notice that vent 102 for the cell 78 may open in a faultevent. As such, to have the substrate board 16 over the vent 102 wouldbe less than optimal. Therefore, as is depicted in FIG. 4A, the way thatthe encapsulated substrate board 92 is arranged with the flex cables 94,96 in such a way that the cell vent 102 is avoided. When theencapsulated substrate board 16 is thermally mounted with the thermallyconductive material 76, then the substrate board 16 is essentially atthe same temperature as the cell can 78, and then an on-chip thermalmeasurement circuit in the processor of the circuit block 46 is able todirectly read the cell temperature, as the processor in the circuitblock 46 is essentially the same temperature as the cell can 78.

Referring again to FIG. 2, it is worth discussing the differentalternatives for the radio in the circuit block 46. It has been alreadymentioned that RF propagation in the PLC mode through the PLC businterface 56 may be utilized. For applications in which the most robustsignal path is through the medium of the high voltage bus, a frequencyband which promotes this propagation mode is the best choice. Forexample, some commercial implementations with carrier frequenciesbetween 455 kHz and 30 MHz are a good choice for the PLC propagationmode. However, if an application is more appropriate for wireless linksbetween the nodes that communicate, then 2.4 GHz is more appropriate. Nolimitations are placed on which frequency band the RF communicationsuse, although usage of frequencies somewhere in the range of 455 kHz to2.4 Ghz would make it easier to find existing solutions from siliconmanufactures. Also, the protocol for the communications is flexibleaccording to the needs of the application. There are some existingprotocols for power line carriers which may be able to be utilized forapplications that make RF links over the wiring. For communications at2.4 Ghz, there are several popular alternatives including Bluetooth andIEEE 802.15.4. No distinctions are made here between the differentprotocols available. An aspect of the use of these communicationprotocols is that they are used to create a data link from the substrateboard 16 to another radio transceiver, to create a data link to thecentral BECM 20. As mentioned above, this may be implemented as a directRF link from the substrate boards to the central BECM 20, or theapproach may utilize mesh networking between the peer substrate boardsin order to create a data link to the central BECM 20.

As mentioned above, the substrate board 16 is a mounting means for theelectronic circuits made of ceramic, FR4, or some other suitable surfaceto mount silicon dies, surface mount components, and everything elsespecified in this text. The connection from Cell 1 to the substrateboard 16 is through the flex cables 94, 96 that can be welded orsoldered on either end. The PLC bus interface 56, power block 48, andcoupler circuit 54 are conventional electronic circuits, formulated ofsurface mount components as appropriate. The crystals 42 and 44 aretypical surface mount devices. The antenna circuit 58 has a number ofalternatives. First, the antenna circuit 58 may be constructed ofstripline, which are the traces on the substrate board 16.Alternatively, for a given application which may require better antennaperformance, a chip antenna may be utilized. For the circuit block 46,the greatest amount of flexibility is called for. The implementation maybe a single monolithic piece of silicon, a Bluetooth Low Energy (BLE)radio, or analog/digital arrays with which to carry out the auxiliaryfunctions. Alternatively, a bare die low cost microprocessor may beused, along with a separate bare die for the radio function. The goal isto find bare die that are commercially available for the processor andradio functions and place these on the substrate board 16 to implementthe function in the most compact and least expensive way. The auxiliaryfunctions as cited in the circuit block 46 are often offered as aperipheral feature along with commercially available embeddedprocessors.

With reference to FIGS. 3 and 5, the monolithic semiconductor 46 thatmeasures cell parameters (e.g., temperature, current, voltage, etc.)data, processes the data, and communicates (wired or wirelessly)information derived therefrom off die is mounted on the (metal) cellcase 78. There are a few mounting methods. The integrated circuit 46 canbe mounted via solder bumps 106 to the (ceramic) substrate 16. Thesubstrate 16 can then be either directly mounted to the cell case 78 viathe thermally conductive adhesive 76, or via a metal tab deposited onthe underside of the substrate 16.

The thermal adhesive use case is for when there is no need to make anelectrical connection from the case 78 to the substrate board 16. Here,the monolithic integrated circuit 46 needs to be mounted with a thermalconnection to the cell can 78. The block 46 is mounted on the substrateboard 16. The substrate board 16 is metallized on the topside (the sidefacing the block 46) with a conductive material such as copper,aluminum, or the like. This metallization layer on the topside ofsubstrate 16 may be patterned via lithographic techniques to createtraces and pads 112, which a die can be mounted on and connected to. Twotechniques for making the node connections are solder bumps 106 on theunderside of the block 46, or a bonding pad on the topside of the block46 which may be wire-bonded to a conductive trace on the substrate board16. Block 114 represents any additional component needed in the circuitalong with the monolithic integrated circuit 46, such as a crystal, atransistor switch, or other components (see FIG. 2).

Referring to FIG. 6, a conductive adhesive mounting is shown. This usecase is for when there is a need to make an electrical connection fromthe metal case 78 to the substrate board 16′. An additionalmetallization layer 116 is added to the bottom side of substrate board16′. Additionally, one or more vias 118 extend from the metallized layer116 to the tracks or circuits 112 on the topside of substrate board 16′.Here, the monolithic integrated circuit 46 needs to be mounted with anelectrical and thermal connection 120 to the cell can 78. The substrateboard 16′ may be prefabricated with metallization layer 112 on the topand the metallization layer 116 on the bottom, which are patternedappropriately before using for mounting the circuits and connecting tothe cell can 78. Here, the layer 120 is an adhesive that is thermallyand electrically conductive, for example, by suspended carbon particlesof appropriate size in the adhesive.

Referring to FIG. 7, a direct die mounting technique is shown. The basicconcept is that the monolithic integrated circuit 46 is directly mountedvia a thermally conductive adhesive 122 onto the metal cell can 78.Here, the die 46 is connected to the cell tabs 98, 100. This will bedone via wire bonds 124, 125. However, the wire bonds 124, 125 need atarget next to the die 46 so they can on one end solder to pad 126 onthe integrated circuit 46; and on the other side, to respective metallicpads 128, 130 on flexible printed circuits 94, 96. The positive weld tab98 on the cell can 78 is joined with the flexible printed circuit 94 viaa weld or solder joint as mentioned above. The flexible printed circuit94 is a flexible circuit trace which is adhesively connected to the cellcan 78. The flexible printed circuit 94 has a conductive trace insideit, but this conductive trace is surrounded by insulative material sothat there is no electrical connection made from it to the metal can 78.So, the node of the positive weld tab 98 is connected to the flexibleprinted circuit 94, and it brings the signal to a spot close to theintegrated circuit 46. The flexible printed circuit 94 has an openingthat exposes this internal metal layer, which the wire bond 124 issoldered or welded to at the pad 128. Similarly, the negative weld tab100 for the cell can 78 is connected to the flexible printed circuit 96via weld or solder joint. The flexible printed circuit 96 brings thenegative cell terminal connection to a spot close to the monolithicintegrated circuit 46. The wire bond 125 connects the pad 126 to the pad130, and this completes the electrical connection of the integratedcircuit 46 to the cell terminals 98, 100. The thermal adhesive 122 makesa good thermal connection from the block 46 to the can 78, butelectrical insulation from the block 46 to the can 78 is desired. So theadhesive 122 is not electrically conductive.

Referring again to FIGS. 3 and 4, the traction battery pack 10 includesthe battery monitoring circuit 46 that measures voltage, temperature,etc. of a single cell (that exclusively powers the monitoring circuit46), and a front-end pass switch 82 (a pass switch positioned betweenthe cell and monitoring circuit) that disconnects power to themonitoring circuit 46 under certain circumstances such as low cellvoltage or an issue detected by a safety monitor, which could beimplemented in software or hardware. Examples of safety monitoringinclude monitoring for overvoltage, overpressure, overcurrent,overtemperature, proper operation of a safety watchdog, etc. Associatedpredefined threshold values can be established through testing orsimulation, for example. Exceeding these threshold values would resultin opening of the pass switch 82.

Referring to FIG. 8, the pass switch concept also can be applied toconventional battery monitoring integrated circuits. Here, we find animplementation of a conventional battery monitoring integrated circuit(BMIC) 136, 138 which have the proposed pass switch applied to them.That is, we apply the pass switch concept to BMIC technology. This isused in a traction battery pack comprised of cells 140, 142 arranged ina string from VC1 to VCmm. There are one or more BMIC's 136, 138 whichmonitor the cells and which communicate the cell voltage readings backto a central controller. Block 144, which is a pass switch circuit, isinterjected between the top cell in a substring and a Vdd pin of theBMIC 136. In this example, the string of 12 cells with the cell 140 atthe bottom and the cell 142 at the top, or cells VC1-VC12, are used topower the BMIC 136 with a reference of the Vss pin of the BMIC 136connected to V_BOT, which is the minus terminal on the cell 140, and thepower connection or the Vdd pin of the BMIC 136 connected to the passswitch circuit. Here, we see that the pass switch circuit 144 opens andcloses the connection from the substring VC1 to VC12 to the power pin orVdd of the BMIC 136. That is, the pass switch circuit 144 can disconnectthe power source from the BMIC 136. Also in this example, every BMIC inthe stack, for example the BMIC the 138, has a similar pass switchcircuit to go with it.

Notice that the pass switch circuit 144 might remind one of the powerswitch circuit 82 in FIG. 3. However, it is not the same. This isbecause the pass switch circuit 82 is optimized for a single-cellbattery pack sensing module peer-to-peer application. The pass switchcircuit 144 is optimized to use with the BMICs 136, 138.

Referring to FIG. 9, power input connection to the block 144 is throughDC_IN+ 148. This corresponds to the positive terminal of the cell 142(VC12). We see also that Vlocal1 150 is connected to the negative pin onthe cell 140 VC1 (VC1/V_BOT), which here is the lowest potential in theoverall cell string VC1 through VCmm. The power source for the passblock comes in via DC_IN+ 148 and Vlocal1 150. The Vlocal1 150 is thereference or local ground and DC_IN+ 148 is the combination power sourceand measurement point for the node at the top of the cell 142 (VC12).The DC_IN+ node 148 connects to a pass transistor 152 in the block 144.The switch 152 is controlled by control block 154. The control block 154measures the voltage of the DC_IN+ 148. It uses this voltage to make thedecision to open the pass switch 152 if the voltage DC_IN+ 148 fallsbelow a certain voltage, for example, 1.0 volt per cell. So, with 12cells VC1 through VC12, 1.0 volt per cell*12 cells=12V. This gives thepossibility of opening the pass switch 152 when the group of 12 cellsVC1 through VC12 falls below an average voltage of IV each. The reasonwhy one might like to do this is because when the cells are that low,the BMIC 144 is likely over discharging these cells to obtain its ownpower. Therefore, it is an excellent protection feature for the controlblock 154 to command the pass switch 152 when the voltage of the DC_IN+148 compared to the Vlocal1 150 falls below for example 12V to protectthe cells against over discharge. There are certain modes of the BMIC136, caused by issues during manufacture or caused by electricaloverstress in the usage of the BMIC 136, that may cause excessivecurrent draw on the Vdd (power) pin of the BMIC 136. In this instance,to prevent issues with the cell string VC1 through VC12, the BMIC 136 isdisconnected using the pass switch circuit 152. Therefore, this providesmuch utility by protecting the cells and allowing replacement of theelectronics module that contains the BMIC 136.

The FSWD is a control input to the control block 154. This FSWD is shownhere as a common signal that connects to a number of pass switchcircuits such as 144, 146. This can be implemented as an interfacesignal that is common and which is able to drive a signal into each ofthe control blocks. For example, a signal which is referenced to theVlocal1 150, also known as V_BOT, can be connected to all the controlblocks through a high impedance or even through optoisolation in eachcontrol block to prevent interaction between the different controlblocks. The FSWD can be connected to a central control module such as aBECM so that in the event of a battery pack safe state event, it maychoose to disconnect all the BMICs by opening all of the pass switches.This is done through the FSWD signal. The central module may send aheartbeat message on the FSWD signal when the system is in a normalstate. But, when the central module does not send a proper heartbeatsignal, the control blocks will then open the pass switches. In thisway, we implement a reliable way for the BMIC to stop drawing power fromthe cells in the event of a safe state event.

In addition, the control blocks may be arranged to open the passswitches under any desired fault event. So far, we have described theusage of the control block 154 to open the pass switch 152 under theevent of undervoltage on the DC_IN+ 148 and as well, the loss of aheartbeat signal on the FSWD. However, there could be any number ofother signals that the control block 154 may decide to monitor foropening the pass switch 152, such as the temperature of the circuitthrough an internal thermistor located in the control block 154, or bymonitoring the current through the pass switch 152 via a measurement ofthe Vds drop of the transistor (not shown), or any other appropriatemeans of noticing that something is wrong in the circuitry.

Referring to FIGS. 10A and 10B, the flex leads 94, 96 (e.g., flexibleflat metal conductors represented by the hatching surrounded by adimensionally controlled insulative material represented by the outlinesurrounding the hatching, with adhesive on one side) are directlyattached to the cell can 78 such that the assembly of the flex leads 94,96 and their attached ground plane can exhibit controlled impedancecharacteristics. Further, the proximity of the flat metal conductorsrelative to an attached ground plane provides electromagnetic shieldingof the flex leads. Thus, the arrangement yields a low Z connection fromthe substrate board 16 to the cell weld tabs 98, 100 and shielding ofthe signal from the weld tabs 98, 100 to the substrate board 16, whichmay facilitate obtaining a low noise, accurate reading from the cell 14.

Two wire bonds 156, 157 connect to a node on the block 46 which is thereference or ground of the transmitter circuit. Wire bond 158 is thenode to connect to the cell+ 98. Wire bond 160 is the node to connect tothe cell− 100. Ground plane 162 is below the plus signal. Notice thatthe ground plane 162 is implemented in a conductor layer of the flexibleprinted circuit 94. The trace on the top of the flexible printed circuit94 only connects to the positive cell terminal 98, and is insulated fromthe ground reference 162. Ground plane 166 is a layer under the flexibleprinted circuit 96. The signal layer in the flexible printed circuit 96connects the wire bond 160 from the cell− connection on the integratedcircuit 46 to the cell tab 100.

The thermal adhesive layer 122 separates the block 46 from the cell can78. It also insulates and prevents any connection from the flexibleprinted circuits 94, 96, and the ground planes 162, 166 to the cell can78: They are all insulated from the can 78. Notice that the groundplanes 162, 166 are connected to each other through their connection viawire bonds 156, 157 to the ground reference of the block 46, but theflexible circuit 94 is not electrically connected to the flexiblecircuit 96. Thus, a stripline antenna which has controlled impedancecharacteristics is formed. It may be used to transmit RF out of thecircuit 46 through the dipole formed by the flexible circuits 94, 96.The ground planes 162, 166 are part of the dipole antenna circuit. Theground plane 162 and flexible printed circuit 94 form a striplineantenna, as do the ground plane 166 and the flexible printed circuit 96.

The processes, methods, or algorithms disclosed herein can bedeliverable to/implemented by a processing device, controller, orcomputer, which can include any existing programmable electronic controlunit or dedicated electronic control unit. Similarly, the processes,methods, or algorithms can be stored as data and instructions executableby a controller or computer in many forms including, but not limited to,information permanently stored on non-writable storage media such asRead Only Memory (ROM) devices and information alterably stored onwriteable storage media such as floppy disks, magnetic tapes, CompactDiscs (CDs), Random Access Memory (RAM) devices, and other magnetic andoptical media. The processes, methods, or algorithms can also beimplemented in a software executable object. Alternatively, theprocesses, methods, or algorithms can be embodied in whole or in partusing suitable hardware components, such as Application SpecificIntegrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs),state machines, controllers or other hardware components or devices, ora combination of hardware, software and firmware components.

The words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the disclosure andclaims. As previously described, the features of various embodiments maybe combined to form further embodiments that may not be explicitlydescribed or illustrated. While various embodiments may have beendescribed as providing advantages or being preferred over otherembodiments or prior art implementations with respect to one or moredesired characteristics, those of ordinary skill in the art recognizethat one or more features or characteristics may be compromised toachieve desired overall system attributes, which depend on the specificapplication and implementation. These attributes include, but are notlimited to cost, strength, durability, life cycle cost, marketability,appearance, packaging, size, serviceability, weight, manufacturability,ease of assembly, etc. As such, embodiments described as less desirablethan other embodiments or prior art implementations with respect to oneor more characteristics are not outside the scope of the disclosure andmay be desirable for particular applications.

What is claimed is:
 1. A battery system comprising: a battery cellincluding a can and tabs; flexible circuits on and electrically isolatedfrom the can, and electrically connected with the tabs; and a monolithicintegrated circuit mounted to the can via thermally conductive adhesivesuch that the can and monolithic integrated circuit are electricallyisolated from one another, wire bonded to the flexible circuits, andconfigured to measure and transmit data about the battery cell.
 2. Thebattery system of claim 1, wherein the monolithic integrated circuitincludes bonding pads electrically connected with the flexible circuits.3. The battery system of claim 1, wherein the data is current data,temperature data, or voltage data.
 4. The battery system of claim 1,wherein the flexible circuits are flexible printed circuits.
 5. Abattery system comprising: a battery cell including a can and tabs;flexible circuits on the can and electrically connected with the tabs;and circuitry adhered to the can, wire bonded to the flexible circuits,and configured to measure and transmit data about the battery cell. 6.The battery system of claim 5, wherein the circuitry is adhered to thecan via a thermally conductive adhesive.
 7. The battery system of claim5, wherein the flexible circuits are electrically isolated from the can.8. The battery system of claim 5, wherein the circuitry includes bondingpads electrically connected with the flexible circuits.
 9. The batterysystem of claim 5, wherein the data is current data, temperature data,or voltage data.
 10. The battery system of claim 5, wherein the flexiblecircuits are flexible printed circuits.
 11. A battery system comprising:a battery cell; flexible circuitry on and electrically isolated from acontainer of the cell, and electrically connected with terminals of thecell; and an integrated circuit adhered to and electrically isolatedfrom the container, wire bonded to the flexible circuits, and configuredto measure and transmit data about the battery cell.
 12. The batterysystem of claim 11, wherein the integrated circuit is adhered to thecontainer via thermally conductive adhesive.
 13. The battery system ofclaim 11, wherein the integrated circuit includes bonding padselectrically connected with the flexible circuits.
 14. The batterysystem of claim 11, wherein the container is a can.
 15. The batterysystem of claim 11, wherein the data is current data, temperature data,or voltage data.
 16. The battery system of claim 11, wherein theflexible circuits are flexible printed circuits.